Speaker:Mr. Karl Breckon, P.E. with BEC
Engineering, FPA Board Member, FPA-SC-08 Subcommittee Chair. Mr.
Breckon graduated from Iowa State University with a B.S. in Construction
Engineering in 1980 and worked for 14 years building major refinery, chemical,
manufacturing, petrochemical, and bridge and road works projects all over
the world. In 2002 Mr. Breckon started BEC Engineering with a partner
to service the foundation repair and foundation construction industry,
including consulting for residential and light industrial projects. He
is Texas licensed professional engineer and a member of the Texas Society
of Professional Engineers, American Society of Civil Engineers, the National
Society of Professional Engineers, and currently serves as a board member
of the Foundation Performance Association.
PRESENTATION
SUMMARY
To an audience of
about 40, Mr. Breckon presented his subcommittee's paper entitled, "Guidelines
for the Specification of Precast Concrete Segmented Piles for Foundation
Underpinning," which successfully completely FPA Peer Review in July
2005.
Mr.
Breckon discussed the scope of the guideline, which addresses design,
manufacturing, and installation recommendations of pre-cast concrete
segmented piles, commonly used for foundation underpinning of existing
residential and other low-rise structures. The guideline addresses both
interconnected and non-interconnected systems. He defined this type
of repair element as a driven displacement pile that relies primarily
on skin friction and which is commonly designed to resist downward movement
(i.e., settlement or subsidence, not heave) only.
Mr. Breckon said
the document was intended to help an owner ensure that repair contractors
hired to raise their foundation meet certain minimum recommended standards,
including:
they should
follow the 15 ASTM standards listed
they should
employ a licensed professional engineer to design the pile layout
they should
maintain maximum pile spacings of 6 - 8 ft depending on the building
height
they should
make certain submittals to the owner, such as initial and final elevation
surveys, pile-driving records, engineered design drawings, safety
program, material test certificates, QA/QC documents, and evidence
of their experience.
they should
use precast segments meeting certain tolerances for diameter, length,
concentricity, hole locations, end-bearing surface flatness, and end-bearing
surface cants.
Minimum warranty
guidelines presented in the paper include:
10 year warranty
period from substantial completion
Warrant to protect
against downward movement only
Warrant repairs
of landscaping and architectural finish damages if repairs of those
damages were included in the original contract
Minimum material
requirements given in the paper include:
28-day compressive
strength of 5000 psi for the concrete
Grade 60 steel
if deformed bars are used for interconnection
Galvanized 7-wire
cable if cable is used for interconnection
Minimum 1/8"
thick shims, but they need not necessarily be steel
37 recommended
installation steps were given in the paper, including:
Perform
an under-slab plumbing leak test before and after lifting
Provide
groundwater and surface water control
Sever
builder's piers after driving the piles, but before lifting the foundation
Drive
one pile at a time unless they are more than 25 ft apart
No pre-drilling
allowed (unless approved by the engineer)
Remove
or abandon piles that meet refusal prior to the engineer's minimum-specified
depth, where refusal is defined as the point where the foundation
elements at the pile are lifted 0.25" - 0.5" above it pre-piled
elevation.
Perform
a final elevation survey within 12 ft of piles
Restore
landscaping
To download Mr.
Breckon's slide presentation, click
here.
To download the
subcommittee's document no. FPA-SC-08-0, click
here.